Japanese Unexamined Patent Application Publication No. 2005-58733 and Japanese Unexamined Patent Application Publication No. 2007-89650 propose an exercise assisting apparatus in the prior art wherein a thigh muscle group is tensed and relaxed with hardly any extension of the knee, by displacing a seat with the user's feet resting on a foot supporting surface and the user's buttocks supported on a contact surface of the seat. This exercise assisting apparatus varies the user's weight acting on the user's legs by changing the ratio of the user's weight supported by a seat by displacing the position of the seat.
By an operation of this kind, the load is reduced compared to a case where the whole weight acts on the user's legs, and the thigh muscles are contracted with hardly any extension of the knee, whereby, for example, even a user having knee pain such as a patient with diabetes is able to strengthen the muscle group of the thigh, and furthermore since the muscle group of the thigh has a large volume, it is also expected to obtain a contribution to improvement in lifestyle-related diseases, by glucose metabolism associated with the muscular contraction. Moreover, by using a drive source to displace the seat, the user is able to exercise passively without exerting muscular force spontaneously, and therefore the load is light and consequently the apparatus can be used even by person's having a low capacity of movement.
An exercise assisting apparatus having the above composition tenses and relaxes the thigh muscle group by changing the weight of the user that acts on the user's legs, with virtually no extension of the knees, and therefore the knee bending angle is an important factor in performing exercise effectively. As the analogy of a squatting movement readily shows, the load acting on the muscle group of the thigh varies with the knee bending angle. Furthermore, in the case of a user with knee pain, if a load acts on the user's knee while the knee is bent to a certain degree, the user often experiences pain and the bending angle must be restricted in order to make an apparatus usable by persons of this type as well.
At the present time, experimental results have been obtained indicating that the exercising effect is high and knee pain is not liable to occur, if the knee bending angle (in practice, the measured angle is that formed between the thigh and the lower leg on the front side of the knee) is set to 140 degrees, and hence this angle has been set as an appropriate angle.
Japanese Patent Application Publication No. 2007-89650 describes a composition which enables adjustment of the position of a seat in such a manner that the knee bending angle becomes a proper angle. The position of the seat when the knee bending angle becomes a proper angle varies depending on the user's physique, and therefore Japanese Patent Application Publication No. 2007-89650 describes, as technology for adjusting the position of the seat, technology whereby users' physiques, such as users' height and weight, are divided into a plurality of classes and the position of the seat is adjusted in stages by designating one of the respective classes, and technology whereby the position of the seat is adjusted continuously by designating a moving direction of the seat.
The former technology has a merit in that usability is good since the position of the seat is adjusted to a proper position simply by the user selecting the range of his or her own physique, but since only the range of height or weight is designated, then it is not possible to achieve adjustments in account of individual differences, and situations where the knee bending angle does not become a proper angle may arise in the case of users who differ significantly from the standard value of leg length.
On the other hand, the latter technology makes it possible to adjust the position of the seat continuously, and therefore it is possible to adjust the knee bending angle to a proper angle, regardless of the length of the user's legs. Furthermore, since the range of height or weight is displayed by combining use of a display device, then it is possible to adjust the position of the seat in such a manner that the knee bending angle becomes a proper angle regardless of the user's physique, by adjusting the seat position to the vicinity of the user's own physique.
However, if there is a large difference between users' physiques when a plurality of users employ the apparatus successively, then the position of the seat must be adjusted continuously by using the display on the display device as a general guide, and the operating time until the seat position has been adjusted in such a manner that the knee bending angle becomes a proper angle may become long.